compare their relative brilliancy; so
that when actual measurements have to be effected by instrumental means,
it is necessary to compare the two stars alternately with some object of
intermediate hue.

[Illustration: Fig. 83.--Perseus and its Neighbouring Stars.]

On the opposite side of the pole to Capella, but not quite so far away,
will be found four small stars in a quadrilateral. They form the head of
the Dragon, the rest of whose form coils right round the pole.

If we continue the curve formed by the three stars g, a, and
d in Perseus, and if we bend round this curve gracefully into one
of an opposite flexion, in the manner shown in Fig. 83, we are first
conducted to two other principal stars in Perseus, marked e and
z. The region of Perseus is one of the richest in the heavens. We
have here a most splendid portion of the Milky Way, and the field of
the telescope is crowded with stars beyond number. Even a small
telescope or an opera-glass directed to this teeming constellation
cannot fail to delight the observer, and convey to him a profound
impression of the extent of the sidereal heavens. We shall give in a
subsequent paragraph a brief enumeration of some of the remarkable
telescopic objects in Perseus. Pursuing in the same figure the line
e and z, we are conducted to the remarkable little group
known as the Pleiades.

[Illustration: Fig. 84.--The Pleiades.]

The Pleiades form a group so universally known and so easily identified
that it hardly seems necessary to give any further specific instructions
for their discovery. It may, however, be observed that in these
latitudes they cannot be seen before midnight during the summer. Let us
suppose that the search is made at about 11 p.m. at night: on the 1st of
January the Pleiades will be found high up in the sky in the south-west;
on the 1st of March, at the same hour, they will be seen to be setting
in the west. On the 1st of May they are not visible; on the 1st of July
they are not visible; on the 1st of September they will be seen low down
in the east. On the 1st of November they will be high in the heavens in
the south-east. On the ensuing 1st of January the Pleiades will be in
the same position as they were on the same date in the previous year,
and so on from year to year. It need, perhaps, hardly be explained here
that these changes are not really due to movements of the
constellations; they are due, of course, to the apparent annual motion
of the